Physicians use finasteride for the treatment of benign prostatic hyperplasia (BPH), informally known as an enlarged prostate. The approved dose is 5 mg once a day, and 6 months or more of treatment with finasteride may be required to determine the therapeutic results of treatment. If the drug is discontinued, any therapeutic benefits will be reversed. Finasteride may improve the symptoms associated with BPH such as difficulty urinating, getting up during the night to urinate, hesitation at the start of urination, and decreased urinary flow.[1]Male pattern baldness

In a 5-year study of men with mild to moderate hair loss, 2 out of 3 of the men who took 1 mg of finasteride daily regrew some hair, as measured by hair counts. In contrast, all of the men in the study who were not taking finasteride lost hair. In the same study, based on photographs that were reviewed by an independent panel of dermatologists, 48% of those treated with finasteride experienced visible regrowth of hair, and a further 42% had no further loss. Average hair count in the treatment group remained above baseline, and showed an increasing difference from hair count in the placebo group, for all five years of the study. Finasteride is effective only for as long as it is taken; the hair gained or maintained is lost within 6â€“12 months of ceasing therapy.[2] In clinical studies, finasteride, like minoxidil, was shown to work on both the crown area and the hairline,[3] but is most successful in the crown area.
Some users, in an effort to save money, buy Proscar (finasteride 5 mg) instead of Propecia, and split the Proscar pills into several parts to approximate the Propecia dosage.[4] The pills are coated to prevent contact with the active ingredient during handling, and the dust or crumbs from broken Proscar tablets should be kept away from pregnant women or women who may become pregnant.[5]Off-label uses
Finasteride is sometimes used as a component of hormone replacement therapy for male-to-female transsexuals in combination with a form of estrogen due to its anti-androgen properties.[6][7] However, little clinical research of finasteride use for this purpose has been conducted and evidence of efficacy is limited. Indeed, finasteride is a substantially weaker anti-androgen in comparison to conventional anti-androgens like spironolactone and cyproterone. Furthermore, it has been associated with inducing depression and anxiety at a high rate in both male and female patients,[8] symptoms that are very common in transsexuals and in whom are already at a high risk for.[9] As a result, prescription of finasteride for this indication in male-to-female transsexuals may not be particularly useful, and could put them at risk for detrimental emotional side effects.

Side effects of finasteride include impotence (1.1% to 18.5%), abnormal ejaculation (7.2%), decreased ejaculatory volume (0.9% to 2.8%), abnormal sexual function (2.5%), gynecomastia (2.2%), erectile dysfunction (1.3%), ejaculation disorder (1.2%) and testicular pain. According to the product package insert, resolution occurred in men who discontinued therapy with finasteride due to these side effects and in most men who continued therapy. The PPI also states that patients have reported persisting erectile dysfunction despite discontinuing the drug. In December 2010, Merck added depression as a side effect of finasteride